Bright light is an important synchronizing agent for the circadian system in humans. Light information reaches the circadian clock (suprachiasmatic nucleus) from the retina via the retinohypothalamic tract and the lateral geniculate body. There is now evidence that the circadian clock receives photic informatoin from non-ocular sources. Recent research has shown that bright light exposure (using bilirubin blankets) to the popliteal region has phase shifting effects on circadian rhythms. The proposed research study will first, determine whether exposure to bright light to the popliteal region, using a novel and practical light source, will have phase shifting effects on the circadian rhythms of core body temperature and melatonin. Secondly, we will test the hypothesis that extraocular light will result in central nervous system activation as evidenced by changes in the electronencephalogram (EEG) and physiological measures such as heart rate and skin temperature.